SAP Calculation Spreadsheet

[VMan]

Hi Guys,
I have spent a little time using the tables in SAP 2009 to set up a simple excel spreadsheet to calculate expected returns for and Pv system.

Could i email a couple of you guys the spreadsheet to see if its correct and what you think could be improved, i will soon be adding more bits but the basic principle is there.

Please PM me your email if you would be knid enough to evaluate this for me.

Thanks

V

 

[VMan]

Taken From Sap 2009:
-------------------
In the UK climate, an installation with 1 kWp typically
produces about 850 kWh of electricity per year (at favourable orientation and not overshaded).

At times of high solar radiation the PV array may generate more electricity than the instantaneous
electricity demand within the dwelling. Arrangements must be made for the surplus electricity to be
exported to the grid via a dual or two-way electricity meter.

The procedure for PV is as follows.

1) Establish the installed peak power of the PV unit (kWp).
2) The electricity produced by the PV module in kWh/year is
0.8 x kWp x S x ZPV
where S is the annual solar radiation from Table H2 (depending on orientation and tilt),
and ZPV is the overshading factor from Table H4.

-----------------

I was assuming the 0.8 came from 800/1000 ( Produing 800w for 1Kwh) so shouldn't this be 0.85 if we get 850w for every 1kw installed?

Did SAP 2005 state we ger 800w per 1Kw installation?? or i am i totaly off the ball with the 0.8?? - if so where do we get 0.8 from??

Thanks

V

 

[yellowvanman]

The difference between SAP2005 and SAP2009 is the values in Table H2 (the S values), don't know what the 0.8 does, I've asked this question myself with no understandable answer. So in answer to your question the equation doesn't need changing from 0.8 to 0.85.

And yes previously 'rule of thumb' 1kWp previously was 800kWh/year and now (using SAP2009) its 850kWh.

 

[VMan]

Cheers yellow,
i will not dwell on it and just take it for what it is.

 

[oslosolar]

i was informed by BRE yesterday that I must use Sap2005 he said due to all the confusion of which sap to use they are going public with a official line and he was fed up with people being refered to him from Mcs helpdesk as they should know

 

[Telegram Sam]

Hi Guys,
I have spent a little time using the tables in SAP 2009 to set up a simple excel spreadsheet to calculate expected returns for and Pv system.

Could i email a couple of you guys the spreadsheet to see if its correct and what you think could be improved, i will soon be adding more bits but the basic principle is there.

Please PM me your email if you would be knid enough to evaluate this for me.

Thanks

V

Could you let me have a copy of the spreadsheet? I am trying to work out the economics of getting solar panels installed and am getting confused by the contradictory info that people are telling me even when standardized under SAP!
Thanks. [email protected]

 

[Earthstore]

Why not post the size of system, orientation (ie south) pitch of roof (in degrees approximate).
I am sure you will get some honest answers for system performance.
Oh yes location in the country if you want a very accurate prediction.

 

[Telegram Sam]

Why not post the size of system, orientation (ie south) pitch of roof (in degrees approximate).
I am sure you will get some honest answers for system performance.
Oh yes location in the country if you want a very accurate prediction.

Yes, been through all this several times but I've been given contradictory answers, I suspect because there are certain parameters (system degradation etc?) that you can vary. Even the base kwh annual outputs allowing for location and so on are different. Which is why I want to check for myself using - I hope - a or the SAP spreadsheet. Hope someone can help out with this.
[Location Co Durham. Orientation: Due south. Shading: Light - Modest. Pitch 25 - 30°]

 

[Earthstore]

You have not put the size (KWP) of proposed system.

degredation has nothing to do with SAP calculations, however if you are looking at returns over 20 or 25 years this can vary enormously just by having a slightly different starting figures then compounding it over the term.

is there any way of avoiding the shading? If not you need a very good system design to negate the effects, it can drag a system down much more than you may have been informed.

i hope this helps.

 

[Telegram Sam]

You have not put the size (KWP) of proposed system.

degredation has nothing to do with SAP calculations, however if you are looking at returns over 20 or 25 years this can vary enormously just by having a slightly different starting figures then compounding it over the term.

is there any way of avoiding the shading? If not you need a very good system design to negate the effects, it can drag a system down much more than you may have been informed.

i hope this helps.

Sorry forgot to mention 4 kwh (not sure about kwp) gross before deductions.
Shading is more or less fixed unless I am going to risk being had up for trespassing. It is however only slight - first thing in the morning and last thing at night.
If I can understand the base output calculation then I should be able to use the spreadsheet to calculate the effect of different degradation figures, amounts of own solar consumption and so on. Provided I can get hold of the basic spreadsheet which I have been shown with all the calculations on it.

 

[Gavin A]

if the company is selling this as a 4kWh system this is not a good sign, as it shows they don't know the correct terminology.

PV systems are rated in units of kWp, which is the peak panel output under standard test conditions.

kWh is a unit of energy - ie 4kW generated for one hour, or 1kW generated for 4 hours.

There are enough decent installers out there who know their onions, no point going with a company that can't even get this right IMO.

 

[Telegram Sam]

if the company is selling this as a 4kWh system this is not a good sign, as it shows they don't know the correct terminology.

PV systems are rated in units of kWp, which is the peak panel output under standard test conditions.

kWh is a unit of energy - ie 4kW generated for one hour, or 1kW generated for 4 hours.

There are enough decent installers out there who know their onions, no point going with a company that can't even get this right IMO.

The mistake in terminology is no doubt mine. I have spoken to a number of installers and all have recommended a 4 kW system without me quizzing them on whether it is kWh or kWp! All I'm trying to do is get hold of the SAP spreadsheet so that I can do some basic number crunching for myself. Can anyone help by providing a copy?

 

[Earthstore]

Are you looking for just year 1, or are you looking for a 20yr projection?
If you are looking to calculate over 20 years what electricity price rises are you going to use? 5%,7% 20% per annum, what inflation rate will you use? 4%,5%.
What drop in system performance, 10%,15% 20%?
Are you going to allow for any repairs during the term? IE a new inverter maybe?
All of these can have an effect on your end result.

I am just trying to help here.

 

[Telegram Sam]

Are you looking for just year 1, or are you looking for a 20yr projection?
If you are looking to calculate over 20 years what electricity price rises are you going to use? 5%,7% 20% per annum, what inflation rate will you use? 4%,5%.
What drop in system performance, 10%,15% 20%?
Are you going to allow for any repairs during the term? IE a new inverter maybe?
All of these can have an effect on your end result.

I am just trying to help here.

Tks. These are precisely the unknowns / variables that I wanted to "crunch" in the spreadsheet, if it exists. Some of the installers who visited me had printouts from the spreadsheet which included various inflation etc assumptions over extended timescales (resulting in different payback periods) and I just want to be able to do my own alternative calculations.

 

[Earthstore]

I am sorry but I can not help with a spreadsheet.

I was involved in the industry, designing and selling systems, even helping to install in the December rush, all of the systems I had installed are producing above the SAP calculation,(even with the summer we had...) this tends to be the norm if the system is designed and installed correctly, and you use the SAP formula correctly.

To be honest, you can crunch the numbers for days on end, and you can come up with whatever 20 year projection that you believe is possible, those in the industry are not sure what the energy prices will do in the next 12 months let alone 20 years, it is possible that we will see a 20% increase in the second half of this year but it could well be a lot less, but as sure as eggs are eggs it will not be going down.

My advice would be to chose an installer that really knows what he is doing, one that works hard to negate the effects of the shading as this will have more effect on your returns than any energy price increase.

Also the prices you quoted up to a point have little reflection as to how good your system will be unless one is using micro inverters, or maybe a Solar Edge system.

Chose wisely, and you will probably make the best investment of your life.

I hope this helps